Modular structure resistant to forced entry and ballistic penetration

ABSTRACT

Disclosed is a structure having an outer shell and an interior, designed for preventing forced entry and providing protection from ballistic projectiles for the occupants, wherein the outer shell includes an outer layer formed of a metal or metal alloys, an intermediate layer formed of a relatively low-density material which aids in slowing incoming ballistic projectiles and absorbing their energy, and an inner layer of lower density than the outer layer but greater density than the intermediate layer, wherein the inner layer has elasticity and is designed to deform upon impact with a ballistic projectile. The structure may include other features, such as additional doors and exterior conduits to admit ducting, wiring or water tubing.

BACKGROUND

Modules resistant to forced entry and ballistic penetration (“MOREFEP”) are used to secure occupants in a number of settings, including providing security for government or embassy personnel, military personnel in the field, and citizens, for home use (“panic rooms”). Occupants can flee to the module in times of perceived danger and seal the structure. The government has requirements for resistance to ballistic penetration in order to receive certification for these structures.

Existing MOREFEPs often use reinforced or hardened “ballistic” steel. The steel generally must be at least about ½″ in thickness to provide an adequate protection level to ballistic penetration. These structures are heavy as a result, and they cannot be readily transported and installed. A structure having a ½ inch steel outer wall, of dimensions 12′×10′×10′, has a weight of about 68,000 pounds

There is thus a need for an MOREFEP which has a reduced weight compared with the existing structures, and provides adequate ballistic and forced entry protection, meeting government specifications.

SUMMARY

A module resistant to forced entry and ballistic penetration is described, where the module has an outer layer formed of a relatively dense, hardened material, including steel or other metals or alloys, and a less dense inner layer which has elasticity and reflects, deflects or otherwise aids in stopping incoming ballistic projectiles. The inner layer is designed to deform upon impact with a ballistic projectile. The structure also includes a low-density intermediate layer, which aids in slowing incoming ballistic projectiles and absorbing their energy.

The outer layer, when struck with a conventional soft-metal (e.g., lead) incoming projectile, deforms it into a shorter flatter object whereupon its energy is more readily absorbed by the intermediate layer, such that it can more easily be stopped by the inner layer. Passage through the outer layer may also induce a projectile to tumble end-over-end, also resulting in its energy being more readily absorbed. The elasticity in the inner layer aids in deflecting or reflecting the ballistic projectile, following its passage (and loss of energy) through the intermediate layer, and the fact that the inner layer deforms, e.g., by fraying on impact, aids significantly in absorbing the projectile's energy.

The inner layer, in one embodiment, is a composite material, Norplex Micarta™-Brass 03 (referring to UL752 Level 3 Ballistic Resistant material), which is a brass-inlaid fiberglass-based material. The outer layer is generally hardened metal or a metal alloy, e.g., ballistic steel plate or aluminum. The intermediate layer may be a fiberglass mesh, including, Rockwool™. Because of the design of the outer and inner layers, in combination with the intermediate layer, the outer layer can be thinner than the conventional outer layers, e.g., it can be ¼″ steel or even ⅛″ steel (or another material or alloy of comparable strength and characteristics) and the structure can still provide Level III protection, meaning stopping of a ballistic projectile of 7.62 mm caliber at a velocity of about 2700 feet per second (fps).

A structure with a ¼″ steel outer wall, an intermediate and inner layers, which was capable of providing level III protection, using steel beams for support and having the dimensions 12′×10′×10+ weighed about 24,000 pounds. Comparably-sized conventional ballistic steel plate structures weigh about three times as much.

If the inner layer is Norplex Micarta BRASS™ (Brass 03), which has inlaid brass cloth, or otherwise includes a metallic layer, the metallic substance provides RF and EMP protection. That is, radio-frequencies cannot penetrate from the outside, thereby preventing electronic eavesdropping. But the RF can get out, for signaling and communication. EMP is a phenomenon associated with proximate nuclear explosions, which can interrupt and disrupt electrical activity and electrical devices.

The structure can also have a number of other features for security and comfort of the occupants, including air conditioning, beds, refrigerators, food preparation areas, and other living accommodations. The weight and dimensions of the preferred structure is such that it can be transported by a C130 transport aircraft to a location. The C130 is the aircraft conventionally used by the United States military for transportation of materiel.

The unit is approvable for government use, and is useful for embassies or other settings where protection from forced entry and ballistic penetration is a concern. It is noted that the determination of protection from ballistic projectiles, as well as determination of the reaction of the structure to warping stresses, was achieved using a computer model.

The frame for the structure can be made of any material or any structure capable of supporting the inner and outer layers; though it is desirable to reduce the weight by using hollow or tubular supports where practical. A frame, consisting of steel beams or other suitable support structures can be used. Alternatively, other means of support, which use fasteners or welding for attachment of the three layers, can be used. The structure can be virtually any shape, but a parallelepiped provides right angle corners and is generally easier to construct.

The structure can be placed inside existing buildings, used in a stand-alone mode, or buried for additional protection from the surrounding earth. Additional properties and the testing of the structure are described below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a MOREFEP structure, partially cut-away.

FIG. 2 is a sectional view of the structure of FIG. 1.

FIG. 3 is a plan view of an exemplary frame for the structure of FIG. 1.

FIG. 4 is a cut-away view of the structure, showing the framing and the alternate exit door.

FIG. 5A shows a sectional view of a corner of the structure of FIG. 1.

FIG. 5B shows a sectional view of a side of the structure of FIG. 4, taken along the lines 5 b-5 b in FIG. 4.

FIG. 6 is a sectional view of a side of the structure of FIG. 4, taken along the lines 6-6.

FIG. 7 shows a sectional view of a side of the structure of FIG. 1, taken along the lines 7-7.

FIG. 8A shows an alternate exit door 14 and door frame 14a suitable for use with the structure of FIG. 1.

FIG. 8B shows a cross-section of the door, taken along the lines A-A in FIG. 8A.

FIG. 8C shows a cross-section of a side of the door, joined to a suitable door frame.

DETAILED DESCRIPTION

One embodiment 10 of the MOREFEP structure is shown in FIG. 1, including a main entry door 12. A sectional plan view is shown in FIG. 2, where the alternate exit door 14 (and main entry door 12) is also shown. Door 14 is designed to be opened from the inside only, and to be used as an exit in the event the main door area is under attack, or otherwise cannot be opened. The main door 12 would typically be equipped with a tumbler system, so that it can be opened using a key or a code from the outside, but not otherwise. Door 14 can use a simpler locking mechanism than door 12, such as movable bolts.

FIG. 3 shows an exemplary frame structure 16 which can be used to support the inner and outer walls of structure 10. The inner and outer layers can be attached to frame 16, either with fasteners or by welding. The frame 16 is preferably a material which is strong enough for support, yet does not add excessive weight. In one embodiment, the frame consists of 4″ square steel tubing. FIG. 4, which is a cut-away view of the structure 10, shows the steel tubing 18, and the inner layer 20 and outer layer 22. Door 14, and the framing 21 a for door 12, is also shown.

FIG. 5A shows a sectional view of the frame for wall 23 and roof 25, with a conduit 24 extending through wall 23. Conduit 24 is designed to accommodate wiring, air conditioning ducting or tubing, or water pipes, to provide external communication. Conduit 24 cannot run in a straight line through the wall 23, as, in such case, it could be penetrated by a ballistic projectile. Conduit 24 does not, however, need to be the same shape shown in FIG. 5A, but can be any shape other than straight.

FIG. 5B shows a sectional view of wall 23, partial section of ceiling 25 and partial section of floor 27. In this embodiment, there are support members 26 and 28 in the ceiling 25 and floor 27, respectively, as well as additional steel tubing support 30.

FIG. 6 is a sectional view of the frame for wall 23, roof 25 and floor 27 (taken along the lines 6-6), where flanges 31-36 are shown. Flanges 31-36 are used to attach to the inner layer 20. Suitable fasteners include Hilti “ZF20THP” series power actuated fasteners, which are inserted following pre-drilling.

FIG. 7 is a sectional view of wall 23, roof 25 and floor 27, showing the inner layer 20, outer layer 22 and insulation layer 21, and the fasteners 31 a attaching the inner layer 20 to the frame. A variety of attachment methods can be used, provided they provide sufficient connection strength to maintain the integrity of the structure during attempted forced entry, ballistic penetration, and/or as required for transportation or during or after installation. For attachment using the W/Hilti ZF201HP series power actuated fasteners, the inner layer 20 is predrilled at each location where a fastener is inserted.

FIG. 8A shows an view of alternate exit door the door 14 from the interior side, having four hinges 20 a, bar 17 a for opening it, and a door closer unit 23. FIG. 8B shows a cross-section of the door 14, having an inner layer 15 a and an outer layer 16 a, which are formed of the same material as the inner and outer layers 20 and 22, respectively. The rock wool insulation is shown in place between the inner and outer layers of the door. FIG. 8C shows the door frame 14 a and door 14 in cross-section, in place, with a hinge 20 a affixed to the frame of structure 10.

At least one door 12 is included in the structure (the embodiment of structure 10 in FIG. 2 has two doors, one being an door 14 for an alternate exit). One suitable example of a main door 12 is the FD160M Bullet and Forced Entry Resistant Door System by Fabrication Designs of Hyattsville, Md. This door includes a predrilled frame to accept anchors, for attachment to the structure. Other door systems may be used, provided that they provide the necessary level of protection once installed.

The structure can be tested using a computer modeling system, as described in Example II below, to determine its response to deformation stresses.

EXAMPLE I Testing of a Wall Construct

In order to determine projectile resistance of the structure walls, a model was constructed, having an inner layer (formed of 0.438″ Norplex Micarta™-Brass 03) an intermediate layer made of Rockwool insulation, and an outer layer of ¼″ ballistic steel. The model was a 12″ by 12″ square, and the intermediate layer was 4″ thick. Three different projectiles were fired from a distance of 20 feet, using a full metal jacketed round. One projectile was a 5.56 mm round, mass of 62 grains, with a muzzle velocity of 2900 fps. A second projectile was a 5.56 mm round, mass of 55 grains, with a muzzle velocity of 3020 fps. The third projectile was a 7.62 mm round, mass of 147 grains, with a muzzle velocity of 2800 fps. Of the three rounds, only the third projectile made any penetration into the inner layer, and that round only penetrated to a level of 3/16″, and did not pierce the inner layer. Accordingly, it was shown that the structure walls provided Level III ballistic protection.

EXAMPLE II Modeling of Structure Deformation

In order to determine if the structure could be transported without subjecting it to stresses of the type that would damage it, a computer simulation model was constructed to model such stresses. Transport loads were assumed to result in a maximum stress of 3,000 psi (from air transport) resulting in a maximum deformation of 0.03 inches. Nevertheless, it was found that because the structure has a high degree of stiffness, there might be issues because of stresses generated during transport, loading or ground handling, which would induce excessive warping of the structure. One can mitigate or eliminate such excessive stresses by including soft padding between the transportation platform and the structure.

It should be understood that the embodiments, examples, terms and expressions used herein are exemplary only and not limiting, and that the scope of the invention is defined only in the claims which follow, and includes all equivalents of the claimed subject matter. 

1. A structure having an outer shell and an interior, for preventing forced entry and providing protection from ballistic projectiles for the occupants, wherein the outer shell comprises: an outer layer formed of a metal or metal alloys, an intermediate layer formed of a relatively low-density material which aids in slowing incoming ballistic projectiles and absorbing their energy, and an inner layer of lower density than the outer layer but greater density than the intermediate layer, wherein the inner layer has elasticity and is designed to deform upon impact with a ballistic projectile.
 2. The structure of claim 1 wherein passing a ballistic projectile through the outer layer induces deformation of the projectile and/or induces it to tumble end-over-end, and the inner layer is designed to fray and separate upon impact by a ballistic projectile.
 3. The structure of claim 1 wherein the outer shell further includes a layer of a metal which interferes with RF and/or EMP so as to shield equipment in the interior of the structure from electronic eavesdropping or EMP.
 4. The structure of claim 1 wherein the outer shell includes at least two openings suitable for installation of doors, and further including doors, one of which can be opened from the outside by a secure means, and one of which can be opened only from the interior.
 5. The structure of claim 1 wherein the outer shell includes an opening permitting interior access but the opening does not run along a straight line.
 6. The structure of claim 5 wherein the opening accommodates wiring, tubing for air conditioning and/or water piping.
 7. The structure of claim 1 which is a parallepiped.
 8. The structure of claim 1 wherein the outer layer is ballistic steel plate, the inner layer is Norplex Micarta™-Brass 03, and the intermediate layer is Rockwool™ insulation.
 9. The structure of claim 8 which provides Level III ballistic protection.
 10. The structure of claim 4 wherein the secure means for the door is a key, combination code, or electronic code.
 11. The structure of claim 4 wherein at least one of the doors is a FD160M Bullet and Forced Entry Resistant Door System by Fabrication Designs of Hyattsville, Md.
 12. The structure of claim 1 wherein, a stress of 3,000 psi, or less, will result in a maximum deformation of 0.03 inches in the outer shell. 